This invention pertains to the art of face-type mechanical seals and more particularly to sealing rotating shafts.
The invention is particularly applicable to sealing a power takeoff shaft in an aircraft engine assembly and will be described with particular reference thereto. However, it will be appreciated that the invention has broader applications and may be advantageously employed in other rotary pump, turbine, or rotary shaft environments and applications.
Face-type mechanical seals are well known and widely used in the industry for sealing rotating shafts under a variety of conditions. Extreme temperatures and pressure ranges can be satisfied with the basic design of a face-type seal merely by altering the types of materials and without straying from the basic design concept of the seal assembly.
By way of example, the assignee of the subject application provides four basic designs of low pressure and high pressure face seals for both normal and extended operating length. Pressure differentials ranging from 0 to 10 PSI or from 0 to 500 PSI can be accommodated without departing from the basic structure of a groove defined in a stationary housing having a wave spring disposed in the base of the groove. A washer is received in the groove and a first surface thereof cooperates with the wave spring. A second face of the washer is operatively engaged by a seal member having a cutout region that accommodates an O-ring for sealing between the seal member and an axially extending surface of the housing groove. The wave spring urges a face of the seal member into operative sealing engagement with the face of a rotary member.
Although face-type seals of this general construction have met with substantial commerical success, certain industries have strict tolerance and sealing requirements due to the nature of the environment. Prior art arrangements have been deemed unable to adequately satisfy these requirements in a simple manner that still maintains ease of manufacture and testing.
The subject invention provides a twin face seal arrangement that meets all of the basic needs of the industry and overcomes the noted objections in a simple, economical manner.